Periodontal disease is a common and widespread disease which has been shown to be a result of pathogenic bacterial infection established within the gingival sulcus. This condition, if not arrested, will deepen to cause formation of a periodontal pocket. The bacteria found in the periodontal pocket are more anaerobic and contain more gram negative organisms than bacteria found supragingivally.
It is known that several factors prevent or impede the treatment of periodontal disease by supragingival application of drugs or other medicaments. For example, the close proximity of the gum tissue to a tooth impairs diffusion of a medicament into a periodontal pocket. Also, a gingival fluid is continually produced in the pocket and flows outwardly. This fluid flows at a rate of about 1 to 5 microliters per hour in healthy periodontal tissues and at a rate of about 10 to 100 microliters per hour in diseased periodontal tissue.
As a result, the penetration of topically or supragingivally applied medicaments has been largely ineffective in the treatment of periodontal disease. Topical application of medicaments typically does not result in penetration of more than 2 mm. into a periodontal pocket. Since periodontal pockets can be about 5 mm. in depth, topical application does not provide any effective means for treatment.
Systematic application of drugs such as tetracycline to periodontal tissue for treatment of the disease is known. Metronidazole on a film of ethylcellulose has been placed in a periodontal pocket for a period of days during which the active agent is slowly released. Then the film must be removed. It is not bioerodible. See U.S. Pat. No. 4,568,535.
Other techniques have also been proposed for treatment of periodontal disease, e.g., capsules or tablets held in the mouth like a throat lozenge, buccal implants, bandages and dressings, topically applied compositions, fibers, dental floss, etc. These techniques, however, are not effective in penetrating the periodontal pocket.
It has also been proposed to insert medicament-impregnated strings or fibers into periodontal pockets to treat the disease. See, for example, U.S. Pat. Nos. 4,406,881 and 4,599,228, incorporated herein by reference. The use of strings or fibers may not result in uniform treatment of the tissue and must be removed by the dentist again at the desired time. These patents also refer to the use of an undiluted paste for treatment of periodontal tissue, the paste being left in place for 10-15 minutes and then removed.
It is also known to use systemic antibiotic treatment to try to control specific pathogenic species. However, use of this treatment results in low concentrations of antibiotic at the site of the periodontal pathogens.
Conventional therapy and treatment of periodontal disease in humans involves the mechanical removal of bacterial plaques and accumulations from the periodontal pocket, often called root planing and scaling. More severe cases may require periodontal surgery to remove damaged tissue. These procedures are expensive, painful, cause extensive bleeding and general discomfort. These procedures are also temporary at best, and frequent recall visits to the dental surgeon are often necessary.